FIGS. 10–12 show a wrench 100 that signals every time its torque reaches a set value. The wrench 100 includes a pipe 102 and a lever 110. The pipe 102 includes first and second open ends and defines a slot 104. The lever 110 includes a first end for engagement with a socket and a second end inserted in the pipe 102. A concave face 112 is formed at the second end of the lever 110. The concave face 112 defines two grooves 114 each for receiving a roller 116. The lever 110 is pivotally connected with the pipe 102 via a pin 120.
A roller 130 is attached to a carriage 132 via a pin 134, and they are put in the pipe 102. The roller 130 is put between the rollers 116. A spring 136 is put in the pipe 102 against the carriage 132. A tube 138 includes a closed end and an open end. A hole 140 is defined in an external face of the tube 138. A thread 142 is formed on an internal face of the tube 138. The tube 138 is put in the pipe 102 against the spring 136. A pin 106 is fit in the hole 140 through the slot 104. Thus the tube 138 is movable but non-rotational in the pipe 102. A spring 144 is put into the tube 138 through the open end. A shaft 146 includes a thread 148 formed thereon. The shaft 146 is put in the pipe 102. The thread 148 is engaged with the thread 142. A bearing 150 is kept in the pipe 102 via two pins 108.
A grip 214 is provided around the pipe 102. The grip 214 includes an enlarged portion 210 extending from an end, a window 211 defined in the enlarged portion 210, a tab 212 extending from the end in the window 211 and an indicator 213 formed on the tab 212. A lens 220 is fit in the window 211. A knob 230 is formed with a scale 231. The knob 230 is attached to the shaft 146.
Rotation of the knob 230 relative to the pipe 102 causes rotation of the shaft 146 relative to the tube 138 so as to change a force between the roller 130 and the rollers 116 via the spring 136. The indicator 213 and the scale 231 show values set for torque in the wrench 100. Every time the torque in the wrench 100 reaches a set value, the roller 130 rolls past one of the rollers 116. Every time this happens, some parts wear. Such wearing eventually affects the precision in setting the values. Hence, insufficient or excessive torque is exerted on a bolt or nut via the wrench 100. This could result in disasters if the wrench 100 is used to make aircrafts for example. To avoid this, the parts must be replaced before they wear out. In practice, replacement is performed after a certain number of times the torque in the wrench 100 reaches the values. To this end, the number of times the torque in the wrench 100 reaches the set values must be counted. However, automatic counting of the number is not possible with the wrench 100.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.